I don't think there is an argument that these certainly look better. I know the 135i kit uses 6 piston brembo manufactured fronts. (For those of you that don't know, the stock 135i front brakes are identical to the yellow BMW "performance brakes", which we already know fit).

Are we talking about the 1M or the regular 135i ???
If you are talking about the 135i, You mean the calipers are 6 pistons, but still on a regular disk/rotors (NOT Cross-drilled OR slotted rotors)
Why don't you just change the Calipers than?